Hakimi J M, Scocca J J
Department of Biochemistry, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205.
J Biol Chem. 1994 Aug 19;269(33):21340-5.
The temperate phage HP1 integrates its genome into the chromosome of Haemophilus influenzae by site-specific recombination between host and phage DNA segments, the attachment sites. This reaction is promoted by the HP1-encoded integrase. The interactions of HP1 integrase with its DNA substrates have been characterized by DNase I footprinting. Two classes of binding sites were identified. At sites of type I, integrase binding almost completely eliminated cleavage by DNase I; type I sites shared the consensus sequence 5'-AGGGATTTWW. At type II sites, integrase binding produced alternating regions of protection from and enhancement of cleavage, suggesting that binding at these sites distorted the DNA. The consensus sequence for type II sites was 5'-ACTGGCGRTW. Each binding site contained two copies of the relevant consensus. The host attachment site (attB) contains an inverted pair of type I consensus sequences surrounding the strand exchange points. The phage attachment site (attP) includes six binding sites, three of type I and three of type II, distributed along its 500 nucleotide pairs. All type I sites contain two consensus motifs arranged as inverted repeats. One of these surrounds the strand exchange points in this substrate, one is located internally, and the third coincides with the right boundary of the attP sequence. One type II site, consisting of an inverted repeat of two type II consensus motifs, coincides with the left boundary of the attP sequence. The other two type II sites contain directly repeated pairs of the consensus and are internally located.
温和噬菌体HP1通过宿主与噬菌体DNA片段（附着位点）之间的位点特异性重组，将其基因组整合到流感嗜血杆菌的染色体中。该反应由HP1编码的整合酶促进。HP1整合酶与其DNA底物的相互作用已通过DNase I足迹法进行了表征。鉴定出两类结合位点。在I型位点，整合酶结合几乎完全消除了DNase I的切割作用；I型位点共有一致序列5'-AGGGATTTWW。在II型位点，整合酶结合产生了交替的受保护和增强切割的区域，这表明在这些位点的结合使DNA发生了扭曲。II型位点的一致序列为5'-ACTGGCGRTW。每个结合位点包含两份相关的一致序列。宿主附着位点（attB）在链交换点周围包含一对反向的I型一致序列。噬菌体附着位点（attP）包括六个结合位点，三个I型和三个II型，沿其500个核苷酸对分布。所有I型位点都包含两个作为反向重复排列的一致基序。其中一个围绕该底物中的链交换点，一个位于内部，第三个与attP序列的右边界重合。一个II型位点由两个II型一致基序的反向重复组成，与attP序列的左边界重合。另外两个II型位点包含直接重复的一致序列对，且位于内部。
